Freeze drying is a water removal process typically used to preserve perishable materials, to extend shelf life or make the material more convenient for transport. Freeze drying principle is based on freezing the material, then reducing the pressure and adding heat to allow the frozen water in the material to sublimate. Freeze-drying process is in contrast to dehydration by most conventional methods that evaporate water using heat.
The direct transition of water from solid to vapor (sublimation), helps to preserve most of the initial raw material's properties such as appearance, shape, taste, color, and flavor. As an important functional property, the freeze-dried product has a high rehydration capacity. However, the main limit to the industrial development is its cost due to the low productivity. Consequently, except the application for biological active material (bacteria, vaccine), the use of freeze-drying is restricted in food industry to high added-value products like coffee, aromatic herbs, etc.
Details of technical specifications are presented in the following Table.
Freeze dryers are used to increase the long term stability of nanomaterials and make nanomaterials development easier.